Conlin Joseph R
The Glencoe Press, 1968
Buku Teks
Nixon, Richard, author
Brown, [date of publication not identified]
Buku Teks
Evera, Stephen Van
[publisher not identified], [date of publication not identified]
Buku Teks
Kyung Hee University Press , 1983
Buku Teks
Frederick A. Praeger, 1960
Buku Teks